This advisory also applies to the corresponding versions of
Kubuntu, Edubuntu, and Xubuntu.

The problem can be corrected by upgrading your system to the
following package versions:

Ubuntu 7.10:
gnome-screensaver 2.20.0-0ubuntu4.2

After a standard system upgrade you need to restart your session to affect
the necessary changes.

Details follow:

Jens Askengren discovered that gnome-screensaver became confused when
running under Compiz, and could lose keyboard lock focus. A local
attacker could exploit this to bypass the user's locked screen saver.